Variations in the macrobenthic invertebrates in relation to physico-chemical characteristics and WQI in Lake Qarun, Egypt

The seasonal relationship between the physico-chemical characteristics and the macrobenthic fauna community was studied in Lake Qarun, Egypt. Lake Qarun receives a huge amount of agricultural drainage water from the neighboring cultivated land via El-Batts and El-Wadi drains. Generally, the obtained results have shown a decrease in dissolved oxygen, transparency and increase in COD, NO₃^– and NH₃ at the stations in front of El-Batts and El-Wadi drains due to the continuous pollutants discharged into the Lake's water. The WQI revealed that the water quality of Lake Qarun is poor for aquatic life. The macrobenthic community consisted of sixteen species belonging to three phyla, Mollusca (7 species) that was dominated by Cerastoderma glaucum, Annelida (4 species) that was dominated by Limnodrillus spp. and Arthropoda (5 species) that was dominated by Balanus pallidus. The structure and abundance of macrobenthic species were affected by many factors especially pollution from the drainage water contaminated with sewages, which affected all living organisms in the Lake. The WQI values of Lake Qarun ranged from 32.30 to 38.40 (poor class) and the average value in the whole area was 35.89 ± 1.64 that is ranked as poor for the aquatic life utilization. To avoid this undesirable effect, the pollutants that flow into the Lake must be treated before being discharged.